11 March 2014

#91 Hormones, role of adrenaline

Hormone is a chemical substance, secreted by endocrine gland, carried by the blood, which alters the activity of one or more  specific  target organs and is then destroyed by the liver.

1. Chemical control of metabolic activity by adrenaline

Adrenaline is a hormone secreted by adrenal glands. When you are frightened, excited, your brain sends impulses along a verve to your adrenal glands. This makes them secrete adrenaline into the blood.

 Adrenal gland is situated above each kidney.

Adrenaline helps you to cope with danger:

1. heart rate supply O2 to brain and muscle more quickly energy for action (fighting, running…).

Contract blood vessels in skin and digestive system they carry very little blood supplies blood back to vital organs (brain and muscles).

2. Stimulate liver to convert glycogen to glucose,  glucose release into the blood by liver extra glucose for muscle help muscle to contract. 

Examples of situations in which adrenaline secretion increases

Adrenaline is needed and secreted in a “fright, fight or flight” situation.

E.g.: When you are facing danger, for example, a masked man with a gun is approaching you.

- Your brain sends a signal to the adrenal glands, to start secreting and pumping adrenaline into the bloodstream.

- the actions of the adrenaline is listed above

- this gets you ready to either stand and fight or run away from the man.

2. Comparison of nervous and hormonal control systems


  1. you could LITERALLY be my new biology teacher...as in the man doesn't teach. I've learnt more here from you than from that man all year

  2. Adrenaline makes the muscles and the liver convert glycogen to glucose. While glucogon only makes the liver convert glycogen to glucose.

  3. I got my exam comin up the day after tmrw. Thanks for this blog. Its pretty useful